Dowd was told not to act on the information yet tipped a childhood friend, identified as J.F., who illicitly made $163,621 on Pharmasset shares, the FBI said. J.F. tipped another friend who made $544,706 on Pharmasset options, the FBI said. In July 2012, agents confronted Dowd, who said he told J.F. to buy stock, while denying he had inside information, the FBI said.

'Dowd admitted that he told J.F., but falsely stated that he had never received information that Pharmasset was going to be acquired by another pharmaceutical company', Paul Fishman, the U.S. attorney in New Jersey, said in a statement.

The number of people sued by the U.S. Securities and Exchange Commission or charged with insider trading by the Justice Department more than doubled since 2008, according to data compiled by Bloomberg. There were 56 in 2008, 96 in 2009, 67 in 2010, 104 in 2011 and 125 last year. Of those, 22 percent were linked to trades involving health-care stocks.